Is the polish sentence correct? If 'moje rodzeństwo ' is third person plural, why is the verb 'je' and not 'jedzą'?
Because "rodzeństwo" is singular in Polish. I know, that's weird, but it's true.
I think of this like the words "family" or "couple" which are singular, but which refer to multiple people.
It's a collective noun:) it involves more than one person but the noun is singular itself!
My mother in law is polish and she calls dinner 'obiad'. Is it because the concept is more related to which meal is the main meal of the day? We don't have light meals in the evening.
Yes, „obiad” is the main meal of the day, eaten usually in the middle of the day or in the afternoon. „Kolacja” is just an evening meal. Some people may refer to late „obiad” as „obiadokolacja”.
I think that in BrE the word "siblings" is very rarely used in this context (and by me, never). "My brothers and sisters" should be accepted.
Added now, together with 'sisters and brothers'. We decided to do it in Tree 2.0, but this is an older sentence.